Frequency changer



April 8,1941 H. M. HUGE FREQUENCY CHANGER Filed lay 6, 1943 2 Sheets-Sheet 1 INVENTDR. HENRY MARTIN HUGE BY M mumms.

April 8, 1947.

H. M HUGE FREQUENCY cru'menn Filed lay 6, 1943 2 Sheets-Sheet LOAD FiG. 7

INVENTOR. HENRY MARTIN HUGE A RNEYS.

Patented Apr. 8, 1 947 I I UNITED STATES PATENT. OFFICE mufiiihm Henry M. Huge, Lorain, Ohio, assignor of onehalf to E. M. Heavens Closman P. Stocker and one-half to Application May 6, 1943, Serial No. 485,833

for producing subharmonic oscillations by shock excitation of a circuit including aninductance with a s'aturable magnetic core is disclosed in a patent to Fallou, 1,633,481, June 21,v 1927. A method for producing self-starting oscillations which are not harmonically related to the input frequency is disclosed in a patent to Heegner,

1,656,195, January 17, 1928.

Some of the principles involved in the Heegner disclosure are utilized in an arrangement shown in a patent to Peterson, 1,884,845, October 25,

1932, in which a discussion of these principles is presented. Briefly, the .Heegner oscillator depends for its operation upon the fact that in a magnetic modulator of the type used, the introduction'of resistance (or losses) at one of the frequencies of the modulation product produces negative resistance at another one of the frequencies. In the Heegner oscillator, the two frequencies at which the circuit oscillates each bear this relation to the other, so that resistance at either one of the frequencies of oscillation is reiiected through the modulator as negative resistance at the other frequency .of oscillation and as positive resistance at the input frequency. The result is that the power supplied at the input frequency divides between the two frequencies of oscillation. Furthermore, any change in the loading or tuning of one of the frequencies ofv oscillation affects both frequencies, and the oscillations are unstable, readily changing in frequency or stopping completely upon slight changes in load or input voltage. In this type of operation, each' of the two frequencies excites the other, while not necessarily exciting itself, and the two frequencies can be termed mutually self-exciting, but this does not necessarily imply that the oscillations are self-startlng. when it is 7 required to supply only one output frequency, this arrangement is inefficient, particularly when the 22 Claims. (CL 172-281) required output frequency is lower than the input frequency.

3;; my invention I overcome both of these disadvantages and am able to supply substantially all of the transformed power to one of the frequencles of oscillation. I accomplish this in some forms of my invention by providing modulating means which absorbs power at the frequency of cases it may be desirable to provide separate modulating means for this purpose. In the arrangements shown, the exchange of power may be bilateral so the load can be drawn at either frequency individually or at both frequencies simultaneously, but this need not always be the 7 case in all embodiments of my invention opposing interactions between the various frequencies which automatically adjust their counteractions to prevent any instability or shift in frequency.

In the first modulating action, resistance introduced at the lower of the two oscillating frequencies may reflect as negative resistance at the higher frequency, and inductance at the lower frequency reflect as capacita ce at the higher frequency. By combining with this action a second action in which resistance at the lowerfrequency reflects as positive resistance at the higher frequency, and inductance reflects as inductance, and by operating the circuit over a range where the opposing effects are substantially balanced, a high degree of stability isobtained, and changes in loading or tuning are I automatically corrected by the circuit without producing changes in frequency. Similarly, additional types of action may be utilized and a balance obtained between the entire combination.

In some forms of my invention the oscillations may be self-starting, while other forms require a starting transient.

In the frequency changer described by Fallou' described in a patent to Stocker, 2,088,618, August 3, 1937, and in this type of converter, a relatively high efficiency can be attained but a shock or starting transient is necessary in order to start the oscillations. Another feature of my invention makes possible the utilization of this type of frequency conversion and eliminates the need for a starting transient. I accomplish this by starting the subharmonic oscillations through the use of mutually self-exciting, self-starting oscillations at two frequencies, but nevertheless utilizing the principle of the Fallen frequency changer once the oscillations are started, thus producing cooperation between two types of frequency changing action. y it is an object of this invention to produce two or more types of frequency changing action in a frequency changer.

Another object of this invention is to produce a self-starting frequency changer of high efficiency.

Another object of this invention is to provide for the exchange of power between two frequencies which are mutally self-exciting'in a magnetic-modulator type frequency changer.

It is another object of this invention to provide a self-starting circuit for a subharmonic generator to eliminate the need for a starting transient.

Another object of this invention is to stabilize I or more frequencies.

An additional object of this invention is to use biased magnetic core means in a balanced arrangement for separating the oscillating currents in a frequency changer producing mutually selfexciting oscillations at two frequencies.

Another object of this invention is to use rectifiers to provide direct current for biasing the magnetic core or cores of a magnetic frequency changer.

Other objects and a better understanding of my invention may be had by referring to th 1- lowing specification and claims, in connection with the accompanying drawings in which Figure 1 is a circuit diagram of a frequency changer made according to my invention, using a bridge arrangement of saturable inductances and a source of direct current for biasing the inductances,

Figure 2' is a modification of Figure 1 including a, relay for starting oscillations,

Figure 3 is another modification of Figure 1 showing auxiliary circuits for starting oscillations,

Figure 4 is an embodiment of my invention without biasing means and without the balanced structure of the previous figures, but including a saturable stabilizing inductance, and a relay for starting oscillations,

Figure 5 is an embodiment of my invention in which the biasing current is applied on the input side of the bridge,

the four saturable inductances of the bridge are ed on two cores and an alternative biasing method is shown, and

Figure 7 is a circuit using rectifiers to supply biasing current, and shows another type of balanced structure replacing the bridge circuit of Figures 1, 2, 3, 5, and 6.

Referring now to Figure 1, there is shown a bridge arrangement made up of saturable inductances l1, l8, I9, and 20, with its input terminals l3 and I4 supplied from a source of alternating current in through a series capacitor ii. The output terminals l5 and ii of the bridge are supplied with biasing current from direct current source ll through inductance 43. The series circult of capacitor 22 and inductance 2| is also connected to the output terminals l5 and ii of the saturable inductance bridge.

I prefer to construct the four saturable inductance I1, l8, l9, and 20 substantially alike to produce a balanced condition between the input terminals l3 and H of the output terminals 15 and I6 Thus, frequencies appearing on the input side of the bridge are normally balanced out of the output side and vice versa.

There is, however, coupling from the input terminals l3, [4 to the output terminals l5, l6 produced :by the biasing current from source II and also by the oscillating current flowing in the circuit of capacitor 22 and inductance 2|. Couplingfrom the output terminals l5, it to the input terminals l3, I4 is produced by current from source I!) and by oscillating current flowing in the input circuit. In other words, the coupling between the two circuits is produced by instantaneous differences in saturation between the various saturable inductances in the bridge, and these differences in saturation are produced by the currents flowing through the inductances. They are referred to as instantaneous differences because they do not in general remain fixed but vary through the cycle of exciting current.

In operation, the frequency changer of Figure l is particularly well adapted to supply load 24 in parallel with capacitor I2 with power at a frequency which is one-third the frequency ofsource I 0 and to supply load 23 in parallel with capacitor 22 with power at a frequency which is two-thirds the frequency of source Ill. The frequency changer of Figure 1 can also be used advantageously to supply load 24 with one-fifththe frequency of source ill and load 23 with four-fifths the frequency of source I0.

Several types of frequency-changing action are produced in the circuit of Figure 1. In this circult, I am able to produce self-starting oscillations by producing mutuall self-exciting currents at the two frequencies of oscillation in the manner previously described. The power supplied at the frequency of source l0 thus divides between the two frequencies. of oscillation and this constitutes one type of frequency changing action.

By producing a second type of action in the same circuit, the operating characteristics are greatly improved. The second action is produced by the frequency multiplying-dividing characteristic of the saturable inductance bridge. This characteristic is dependent on the biasing current to a great extent, and when voltage of a given frequency is impressed across input terminals I3, I 4, voltages of even multiples of this frequency appear across the output terminals IE, IS, With the voltage present on both sides of the bridge,

the power can flow in either direction, from the low frequency on the input side of the bridge to the frequency changer. With this action cooperating with the first type of action the input power which originally divided between the two frequencies can be shifted to either one of the frequencies as the loads mayrequire.

A third type of action occurring in the circuit of Figure l is of the type produced in the Fallou subharmonic generator previously mentioned. This third type of action occurs in the primary circuit of source i0, capacitor l2, and the saturable inductance bridge from terminal I! to terminal l4. Although this type of action would otherwise require a starting transient the oscillations are started by the first type as previously described. The cooperation between the first type and the third type of frequency changing action produces what can be described as a 1 method for starting the oscillations in a subharmonic generator without the use of a starting transient by the use of an auxiliary circuit producing oscillations mutually self-exciting with the subharmonic oscillations, The second and third types of frequency changing action cooperating with each other provide efilcient and stable means capable of supplying power either to load 24 or to load 23 or to both.

start the oscillations in those cases where they are not self-starting. The frequency changer of Figure 2 is particularly adaptable for supplying load 24 with a frequency one-fifth the frequency of source I and load 23 with a frequency twofifths the frequency of source l0. As in Figure 1,

the cooperation between the several types of frequency changing action occurring increases the efficiency, maintains the stability of operation, and makes it possible to supply load at either one or; the frequencies individually or at both simultaneously.

The normally closed contacts of relay 44 unbalance the bridge and by shorting inductance i9 produce suillcient current flow through the relay winding to operate it, opening the contacts and setting the stage for normal circuit operation. When the circuit impedances have values ,within the operating range, the shock produced by the relay operation starts the oscillations, and the contacts of relay 44 are held open as long as the oscillations continue. 1

The method of connecting relay 44 ,is shown merely as an eicample. Other methods of connecting the relay can also be used effectively, for example the contacts might be usedto short terminals i3 and I4 instead of i4 and I5, or the relay winding might be inserted in series with inductance 2| instead of in series with source Ill. The frequency changer of Figure 2 operates in substantially the same manner as that of Figure 1 once the oscillations are started, except that I the relay for starting would ordinarily be used when the two frequencies of oscillation are such that self-starting is not normall obtained. as in the example given, where the frequencies are one-fifth and two-fifths the source frequency. Although self-starting may not be obtained, nevertheless 'a mutually self-exciting type of frequency changing action in which the input power divides between two frequencies of oscillation is still present. This action in cooperation with the other types of frequency-changing present cooperate to produce high efllciency and stability and to produce other advantages as explained in connection with Figure 1.

Figure 3 shows an arrangement I have found to be satisfactory for starting the oscillations .when load 24 is supplied with one-fifth the frequency of source i0 and load 23 is supplied with two-fifths the frequency of source ID. The starting arrangement is an auxiliary self-exciting circult and comprises capacitor 45 connected to output terminals [5 and I5 and the series combination of capacitor 48 and inductance 41 connected to output terminals i5 and it. These elements changing actions utilized in the arrangement of Figure 2 become effective.

Figure 4 is the circuit diagram of an embodiment of my invention utilizing unbiased saturable inductances. Thegarrangement shown is particularly adapted to supply load 24 with power at a frequency one-fifth the frequency of source l9. and load 29 with power at a frequency threefifths the frequency of source Ill.

The normally closed contacts of relay 44 shunt saturable inductance 48 and charge capacitors 53 and 54. The charging current of capacitors 53 and 54 passes through the winding of relay 44 and opens the relay contacts putting saturable inductance 48 in the circuit in series with alternating current source l0. saturable inductance windings 55 and 55 act to step up the voltage supplied i'io capacitors 53 and 54 and inductances 49 and 5 The term inductance as used herein does not exclude the possible use of the windings of the unit so designated as a transformer, but implies that the action of the unit depends on its exciting current. This is in contrast to the term transformer" which usually implies that the exciting current of the unit is merely incidental to its operation. Thus. substantially linear inductances 49 and 5| are used as transformers I having secondary windings 59 and 52.-

The use of winding 56 to increase the voltage supplied to the capacitors 53 and 54 and inductances 49 and 5| produces an advantage when source i0 is the commercial 115-volt supply in permitting the use of smaller high voltage capacitors instead of the large low-voltage capacitors which would be required if capacitors 53 and 54 were supplied from the voltage across one-fifth the frequency of source I and a component of three-fifths the frequency of source l0. saturable inductance 48 in cooperation with the other circuit elements acts to convert power from source In to power at the lower frequencies. The voltage across saturable inductance windin 55, and consequently across output winding 51 includes components of both one-fifth and threefifths the source frequency, therefore in order to supply load 24 with a relatively undistorted voltage wave of one-fifth the source frequency, I prefer to connect in series with winding 51 another winding across which voltage of threefifths the source frequency appears, phasing the windings to reduce the voltage of three-fifths the source frequency which is supplied to load 24. Figure 4 shows this voltage supplied from substantially linear inductance 5| by means of an insulated winding 52. Since both inductance 9 and inductance 5| have voltage of this frequency across them, the wave-shape correcting voltage could be supplied from inductance 49 if preferred. Under some conditions linear inductance 51 may be omitted, and when this is the case, the insulated secondary winding 52 can be wound on linear inductance 49, along with secondary winding 50.

Load 23 is supplied with voltage of three-fifths the frequency of source If! supplied from inductance 49 by means of the insulated winding 50. For load 23 the wave-shape correcting voltage is supplied from secondary winding 58.

In the arrangement of Figure 4 a first type of frequency changing action occurs in the generation of the fifth subharmonic of the frequency of source Hi. This action is of the type produced in the Fallon subharmonic generator previously mentioned, and in the circuit arrangement shown,

some of the advantages of the frequency changer described in the patent to Stocker, 2,088,618, are obtained.

A second type of frequency changing action occurs through the interaction of three voltages across saturable inductance 48, the one voltage being of the source frequency, the second being one-fifth the source frequency and the third three-fifths the frequency of source Hi. In this action the power supplied at the source frequency is converted to the other two mutually self-exciting frequencies and divides between them.

A third type of frequency-changing action is the frequency tripling action which can convert power from one-fifth the source frequency to three-fifths the source frequency, or, when acting in the opposite direction. from three-fifths to one-fifth the source frequency.

Thus the arrangement of Figure 4 is an embodiment of my invention utilizing several types of frequency changing action in cooperation with each other to stabilize the operation of the frequency changer and to produce the desirable operating characteristics described in connection with Figures 1,2, and 3.

Figure 5 is the circuit diagram of a frequency reducing arrangement comprising a saturable inductance bridge with direct-current bias supplied to the input terminals. This arrangement is best adapted to supply load 24 with power at a frequency which is an even-numbered submultiple of the frequency of source i0 and to supply load 23 with power at a frequency which is an odd multiple of one-half the frequency supplied to load 24. Thus it is possible with this arrangement to supply load 73 with one-fourth the frequency of source it and load 23 with threeeighths the frequency of source I II. The input circuit comprising substantially linear inductance 62, source HI, capacitor l2 and the input terminals l3 and ll of the saturable ind c nc bridge in series, together with the. biasing arrangement comprising direct current source il in series. with inductance 83 represents a frequency dividing arrangement in which a first type of frequency-changing action may occur, that is the conversion from the source frequency to one-fourth the source frequency. f

The biased saturable inductance bridge together with capacitors 59 and 60 and inductance 6| connected to output terminals I! and II represents a frequency changing circuit in which several more types of frequency-changing action may occur, through the cooperation of capacitor i2 and inductances 62 and 63. One action is the conversion between one-fourth the frequency of source in across terminals I 3 and I 4 and threeeighths the frequency of source l0 across terminals l5 and I6, another is the conversion between three-fourths the source frequency across terminals l3 and i4 and three-eighths the source frequency across terminals l5 and i6.

These actions represent some of the channels through which power can be interchanged between the several frequencies of oscillation. Because of this interchange of power the oscillations are stabilized and the power is supplied where it is needed.

In addition to the interchange of power between the various frequencies of oscillation, other types of frequency changing action occur in which the interaction between the voltages of the frequencies of oscillation and the voltage of the source frequency across the saturable inductances produces a. conversion of power from the source frequency to the oscillating frequencies.

The circuit of Figure 6 is a modification of the circuit of Figure 1. The four inductances, H, II, l9 and 20, of the saturable inductance bridge are combined on two saturable cores 25 and 28 in Figure 6. Because of the symmetry of the arrangement in Figure 1, the voltage across inductance I1 is substantially the same as that across inductance l9, and the voltage across inductance i8 is substantially the same as that across inductance 20, therefore by putting inductances I! and IS on the common core 25 and winding them with substantially the same number of turns and putting inductances l8 and 20 on the common core 26 with substantially equal windings, no essential change in circuit operation is produced. I prefer to construct cores 25 and 28 substantially alike and all four inductances with substantially the same number of turns.

In Figure 6 as in Figure 1, the junction between inductances l1 and 20 is designated input terminal IS, the junction between I! and I8 is output terminal ii, the junction between I8 and I8 is input terminal l4, and the junction between l8 and 20 is output terminal 16. The balanced relationship between output terminals l5 and II and input terminals l3 and I4 is substantially the same in Figure 6 as in Figure 1.

. The arrangement of Figure 6 is frequently more economical, both in space and in cost than that of Figure 1 because it substitutes two units for the four somewhat smaller units required in Figure 1.

The biasing arrangement of Figure 6 supplies the biasing current to output terminals II and IQ of the saturable inductance bridge as does direct current source H in Figure 1. In Figure 6,

however, the biasing source II is in seri s with the tuning elements 2| and 22 and therefore the alternating current of the secondary circuit passes through source The direct current from source H which biases the magnetic cores 2! and 26 passes through inductance 2| and through transformer winding 21 in parallellwith capacitor 22; Load 23 is supplied from the voltage across capacitor 22 through the insulating transformer secondary winding 28; this arrangement insulates the load from the direct current source H and the alternating current source In, and at the same time provides a convenient method for obtaining the required output voltage by providing the proper turn ratio between windings 21 and 28.

In operation, the circuit of Figure 6 exhibits substantially the same characteristics and D- erates in substantially the same manner as the circuit of Figure 1.

The modifications shown in Figure 6 can, for the most part, be applied to Figures 2, 3, and as well as to Figure 1.

Figure '7 is another modification of the circuits of Figures 1 and 6. In Figure 7 a third type of balanced arrangement of saturable inductances is shown. In this arrangement the input circuit is not conductively connected to the output circuit as it was in the previous arrangements, but the balanced relationship between the input and the output circuits of the saturable inductances is substantially the same as in the circuits of Figures 1, 2, 3, 5 and 6.

saturable cores 25 and 26 are preferably constructed substantially alike and windings 29 and 30 preferably have substantially the same number of turns. Windings 3| and 32 are preferably made with a substantially equal number of turns and they are connected in series oppositelyto the series connection of input windings 29 and 30, so that capacitor 22 and inductance 2| are in substantially the same electrical relationship to the source as they are in Figure 6, that is, they are on the output side of the balanced structure.

The load 24 in Figure '7 is effectively on the input side of the balanced circuit, because the substantially equal windings 35 and 36 are connected in the same polarity as input windings 29 and 30. In Figure 6 the load 24 connected across capacitor l2 received a relatively small voltage of the frequency of source Hi. In Figure 7 an arrangement is shown which makes it possible to minimize the voltage from source ill in the voltage supplied to load 24 or to adjust it to any other required value. This is accomplished by connecting, secondary winding 42 on transformer 39 in series with load 24, supplying a voltage from source l0 which can be set to the proper direction and magnitude to neutralize most of the voltage of the frequency of source it! which appears across windings 35 and 36. Thus in the arrangement of Figure '7 load 24 can be su plied with a voltage of the same frequency as in Figure 6 and a somewhat lower harmonic content, if required. In addition, the windings in Figure '7 can be proportioned to give any required output voltage and the load is insulated from the source ID.

' Load 23 is effectively on the output side of the balanced circuit, because substantially equal windings 33 and 34 ar connected in series in the same polarity as windings 3| and 32. Thus load 23 can be supplied with the same frequency as load 23 in Figure 6. If a reduced harmonic content in the voltage to load 23 were required, an additional winding, not shown, on inductance 2| could be connected in series with windings 32 and 34 to provide a wave shape correcting voltage.

The biasing current in Figure '7 is supplied by the rectifiersfl, energized from secondary winding 4| on transformer 39 whose primary winding 40 is energized from source i0. Similarly, rectifiers can be substituted for direct current source il in Figures 1, 2, 3, 5, and 6, The rectifiers supply direct current through inductance 43, and a capacitor 38 is shown across the rectifier output, for filtering purposes. Capacitor 38 may be omitted if preferred.

The operation of the frequency changer of Figure 7 is substantially the same as the frequency changer of Figure 1. The balanced circuit shown in Figure '7 can be used in the circuits of Figures 2, 3, 5, and 6 as well as Figure 1.

Other balanced circuits can also be used in place of the balanced arrangements shown. For example, saturable inductance windings can be arranged on a common core and a balance of magnetizing forces substituted forthe balance of electromotive forces obtained in the circuits of Figures 1, 2, 3, 5, and 6.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

I claim as my invention:

1. A frequency changer adapted to be energized by a source of alternating current, comprising in combination, a plurality of saturable incluctances connected in a substantially balanced combination having a pair of input terminals and a pair of output terminals, coupling between said input terminals and said output terminals varying in response to instantaneous differences in saturation between different members of said plurality of saturable inductances, primary circuit means, including a first capacitor. connected to said input terminals, secondary circuit means, including a second capacitor, connected to said output terminals, and a source-of direct current connected in said secondary circuit means, said frequency changer being adapted to produce across said input terminals voltage of the frequency of said source of alternating current and of an odd subharmonic of that frequencyand to produce across said output terminals voltage of a frequency which is an even harmonic of said odd subhar- I monic.

2. A frequency changer adapted to be energized by a source of alternating current, comprising in combination, a plurality of saturable inductances connected in a substantially balanced combination having a pair of input terminals and a pair of output terminals, coupling between said input terminals and said output terminals varying in response to instantaneous differences in saturation between different members of said plurality of saturable inductances, primary circuit means, including a first capacitor, connected to said input terminals, secondary circuit means, including a second capacitor, connected to said output terminals, and a source of direct current connected in said primary circuit means, said frequency changer being adapted to produce across said input terminals voltage of the frequency of said source of alternating current and of an even subharmonic of that frequency and to produce across said ou put terminals, voltage of a frequency which is an odd multiple of one-half said even subharmonic frequency.

3. A frequency changer adapted to be energized by a source of alternating current, comprising in combination a plurality of saturable inductances connected in a substantially balanced combination having a pair of input terminals and a pair of output terminals, coupling between said input terminals and said output terminals varying in response to instantaneous differences in saturation between different members of said plurality of saturable inductances, primary circuit means, including a first capacitor, connected to said input terminals, secondary circuit means, including a second capacitor, connected to said output terminals, and a source of direct current connected in said secondary circuit means, said frequency changer being adapted to produce across said input terminals voltage of the frequency of said source of alternating current and of an odd subharmonic of that frequency and to produce across said output terminals voltage of a' frequency which is an even harmonic of said odd subharmonic, and primary circuit output means adapted to supply a load with voltage of said odd subharmonic frequency.

4. A frequency changer adapted to he energized by a source of alternating current, comprising in combination, a plurality of saturable inductances connected in a substantially balanced combination having a pair of input terminals and a pair of output terminals, coupling between said input terminals and said output terminals varying in response to instantaneous differences in saturation between different members of said plurality of saturable inductances, primary circuit means, including a first capacitor, connected to said input terminals, secondary circuit means, including a second capacitor, connected to said output terminals, and a source of direct current connected in said secondary circuit means, said frequency changer being adapted to produce across said input terminals voltage of the frequency of said source of alternating current and of an odd subharmonic of that frequency and to produce across said output terminals voltage of a frequency which is an even harmonic of said odd subharmonic, and secondary circuit output means adapted to supply a load with voltage of said even harmonic of the odd subharmonic frequency.

5. A frequency changer adapted to be energized by a source of alternating current, comprising in combination, a plurality of saturable inductances connected in a substantially balanced combination having a pair of input terminals and a pair of output terminals coupling between said input terminals and said output terminals varying in response to instantaneous differences in saturation between different members of said plurality of saturable inductances, primary circuit means, including a first capacitor, connected to said input terminals, secondary circuit means, including a second capacitor, connected to said output terminals, and a source of direct current connected in said primary circuit means, said frequency changer being adapted to produce across said input terminals voltage of the frequency of said source of alternating current and of an even subharmonic of that frequency and to produce across said output terminals, voltage of a frequency which is an odd multiple of one-half said even subharmonic frequency and primary circuit out ut means adapted to supply a load with volt age of said even subharmonic frequency. l

6. A frequency changer adapted to be enersized by a source of alternating current, comprising in combination, a plurality of saturable inductances connected in a substantially balanced combination having a pair of input terminals and a pair of output terminals coupling between said input terminals and said output terminals varying in response to instantaneous differenzes in saturation between different members of said plurality of saturable inductances, primary circuit means, including a first capacitor, connected to said input terminals, secondary circ'uit means, including a second capacitor, connected to said output terminals, and a source of direct current connected in said primary circuit means, said frequency changer being adapted to produce across said input terminals voltage of the frequency of said source of alternating current and of an even subharmonic of that frequency and to produce across said output terminals, voltage of a frequency which is anodd multiple of one-half said even subharmonic frequency and secondary circuit output means adapted to supply a load with voltage of said odd multiple of one-half the even subharmonic frequency, and secondary circuit output means adapted to supply a load with voltage of said odd multiple of one-half the even subharmonic frequency.

7. A frequency changer adapted to be energized by a source of alternating current, comprising in combination, a plurality of saturable in duztances connected in a substantially balanced combination having a pair of input terminals and a pair of output terminals, coupling between said input terminals and said output terminals varying in response to instantaneous differences in saturation between different members of said plurality of saturable inductances, primary circuit means, including a. firstcapacitor, connected to said input terminals, secondary circuit means,

including a second capa3itor, connected to said output terminals, and a source of direct current connected in said secondary circuit means, said frequency changer being adapted to produce across said input terminals voltage of the frequency of said source of alternating current and of an odd subharmonic of that frequency and to produce across said output terminals voltage of a frequency which is an even harmonic of said odd subharmonic, primary circuit output means adapted to supply a load with voltage of said odd subharmonic frequency and secondary circuit output means adapted to supply a load with voltage of said even harmonic of the odd subharmonic frequency.

8. A frequency changer adapted to be energized by a source of alternating curren comprising in combination, a plurality of saturable inductances connected in a substantially balanced combination having a pair of input terminals and a pair of output terminals coupling between said input terminals and said output terminals varying in response to instantaneous differences in saturation between different members of said plurality of saturable inductances, primary circuit means, including a first capacltor, connected to said input terminals, secondary circuit means, including a second capacitor, connected to said output terminals, and a source of direct current connected in said primary circuit means, said frequency changer being adapted to produce across said input terminals voltage of the frequency of said source of alternating current and of an even subharmonic of that frequency and to produce across said output termeans adapted to supply a load with voltage of said odd multiple of one-half the even subharmonic frequency.

9. A frequency changer adapted to be energized by a source of alternating current, comprising in combination a first saturable inductance adapted to be connected in series with said source of alternating current, a second saturable inductance connected in series with the first saturable inductance, capacitive circuit means substantially in parallel with said second saturable inductance, said capacitive circuit means comprising a first capacitor substantially in parallel with the second saturable inductance, a second capacitor in series with a substantially linear inductance in a series combination, said series combination being substantially in parallel with the second saturable inductance, and output circuit means adapted to supply a load with voltage of one-fifth the fre quency of said source of alternating current.

10. A frequency changer adapted to be energized by a source of alternating current. comprising in combination a first. saturable inductance adapted to be connected in series with said source of alternating current, a second saturable inductance connected in series with the first saturable inductance, capacitive circuit means substantially in parallel with said second saturable inductance, said capacitive circuit means comprising a first capacitor substantially in parallel with the second saturable inductance, a second capacitor in series with a substantially linear inductance in a series combination, said series combination being substantially in parallel with the second saturable inductance, and output circuit means adapted to supply a load with voltageof three-fifths the frequency of said source of alternating current.

11. In a magnetic frequency-changer producing mutually self-exciting oscillations at two fresov quencies different from the frequency of the energizing source, circuit means adapted to separate the oscillations of the two frequencies from each other, said circuit means comprising a plurality of saturable inductances in a substantially balanced combination having a pair of input terminals and a pair of output terminals, and biasing means producing unidirectional flux in said saturable inductances, one of said two frequencies appearing at the input terminals, the other at the output terminals of said substantially balanced combination.

12. In a magnetic frequency-changer produc- .ing mutually self-exciting oscillations at a plurality of frequencies different from the frequency of its energizing source, saturable magnetic core means and winding means thereon, said winding means being energized by at least two of said plurality of frequencies, said winding means producing in said saturable magnetic core means super-imposed fluxes of the said two frequencies to convert power from one to the other.

13. In a frequency changer utilizing saturable magnetic core means for producing subharmonic oscillations in a circuit coupled to said core means, circuit means comprising an auxiliary exciting circuit coupled to the core means and adapted to produce oscillations at a frequency mutually self-exciting with the subharmonic frequency, to self-start the subharmonic oscillations.

'14. In combination with a frequency changing circuit utilizing saturable magnetic core means for produ cing subharmonic oscillations in a circuit coupled to the core means, exciting means comprising-an auxiliary exciting circuit coupled to the core means and adapted to produce oscillations mutually self-exciting with the subharmonicoscillations.

15. In a frequency changer utilizing saturable magnetic core means for producing subharmonic oscillations in a circuit coupled to said core means, circuit means comprising an auxiliary exciting circuit coupled to the core means and adapted to produce oscillations at a frequency I which is a harmonic of said subharmonic and adapted to produce oscillations at said harmbnic frequency to self-start the subharmonic oscillations.

auxiliary exciting circuit coupled to the core r means and adapted to produce oscillations atsa frequency equal to twice the frequency of the source minus the subharmonic frequency, to selfstart the subharmonic oscillations.

18. In combination with a frequency changing circuit adapted to be energized by an alternating current source and utilizing saturable magnetic core means for producing subharmonic oscillations in a circuit coupled to the core means, exciting means comprising an auxiliary exciting circuit coupled to the core means and adapted to produce oscillations of a frequency equal to twice the frequency of the source minus the subharmonic frequency.

19. In a frequency changer adapted to be energized by an alternating current source and utilizing saturable magnetic core means for producing subharmonic oscillations in a circuit coupled to said core means, circuit means comprising an auxiliary exciting circuit coupled to the core means and adapted to produce oscillations at a frequency equal to the frequency of said source minus the subharmonic frequency to selfestart the subharmonic oscillations, said circuit means further comprising biasing means for producing unidirectional flux in said core means.

20. In combination with a frequency changing circuit adapted to be energized by an alternating current source and utilizing saturable magnetic core means for producing subharmonic oscillations in a circuit coupled to the core means, exciting means comprising an auxiliary exciting circuit coupled to the core means and adapted to produce oscillations of a frequency equal to the frequency of said source minus the subharmonic frequency, said exciting means further comprising biasing means for producing unidirectional flux in said core means.

21. In combination with a frequency changing circuit adapted to be energized by an alternating current source and utilizing saturable magnetic core means for producing subharmonic oscillations in a. circuit coupledto the core means, ex-

citing means comprising an auxiliary exciting circuit coupled to the core means and adapted to produce oscillations of a. frequency equal to the frequency of said source minus twice the subharmonic frequency.

22. In combination with a frequency changing circuit adapted to be energized by an alternating current source and utilizing saturable magnetic core means for producing subharmonic oscillations in a circuit coupled to the core means, exciting means comprising an auxiliary exciting circuit coupled to the core means and adapted to produce oscillations of a frequency equal to onehalf the frequency of the source minus one-half the subharmonic frequency.

. HENRY M. HUGE.

REFERENCES CITED The following references are of record in the 5 file of this patent:

UNITED STATES PATENTS Peterson Apr. 27, 1943 

